Peters



(No Model.)

G. H. PEGRAM. UONTINUOUS GIRDBR BRIDGE.

No. 424,349. Patented'MaJr. 25, 1890.

inveni'or:

IL FEYER5 Phony-Lithograph Wauhinpon. D. C

NITED STATES PATENT OrFicE.

GEORGE H. PEGRAM, OF NEW YORK, N. Y.

CONTlNUOUS-GIRDER BRIDGE.

SPECIFICATION forming part of Letters Patent No. 424,349, dated March25, 1890.

Application filed November 11, 1887- Serial No. 254,878. (No model.)

To aZZ whom it may concern:

Be it known that I, GEORGE H. PEGRAM, of the city, county, and State ofNew York, haveinvented anImprovementin Continuous- Girder Bridges, ofwhich the following is a specification.

My invention consists of an improvement in continuous-girder bridgesthrough which advantages of cost and construction are gained, and isessentially the combination of through and deck spans, as shown in theaccompanying drawings and described in the following specification.

The object of my invention is to so form a girder bridge that it may becheaply erected and yet attain all of the advantages of the expensivemodes of construction now in use.

My invention comprehends the combination of the deck and through spanswhen one at least of the two are made as a cantalevertruss to act as asupport for the other while building and when built. The terms deck andthrough spans are used in the general sense, a deck-span beingunderstood to be a truss-span .in which the roadway practically conformsto the grade and elevation of the top chord of the bridge and athrough-span one in which the grade andelevation of the roadwaypractically conform to the bottom chord. An arch bridge in whichportions of the arch or bracing rise above the level of the roadwaywhile portions are below it is not to be construed as a combination ofdeck and through spans in the sense in which the terms are used in thisapplication, even if the portions are divided by hinges. Thus thedeckspans may be the cantalevers or the throughspans may be constructedas the cantalevers; but I prefer the former. The advantages of thisconstruction will be apparent when we consider that heretofore to obtaingreat clearance above high water it was necessary to build athrough-span supported on the piers, and at great expense in false Workused during construction; also, when we consider that to obtain a widewater-way between piers with at least a small portion of the width ofgreat height or clearance an excessively long through-span wasnecessary. In my impro vement only a shallow false work is required, andthat, too, Where the river is most shallow, and after building thedeck-spans upon short piers, the adjacent ends of such spans arecontinued out over the main water-way toward each other without falsework, and thus form eantalevers, and upon these cantalevers thethrough-span is supported. This throughspan is much less in length thanthe width of the water-way, and hence its height between chords is alsoless and the structure as an entirety cheapened without in the leastreducing its effieiency. Furthermore, this througlrspan may be erectedupon a temporary truss hung from the two cantalevers, and thus the useof false work obviated. Even in the largest through-spans of thisconstruction a single temporary pier alone would be required. The costof a bridge in a' large measure depends upon the cost of this falseWork, and hence dispensing with its use in those parts of the riverwhere the deepest Water or channel exists is a feature of greatimportance. truss for those parts of the bridge which rest upon thepiers reduces the cost of such piers by reducing the height required,and hence in certain types of my invention the advan tages to be gainedare more apparent than in others.

In the drawings, Figure 1 is a side elevation of my preferred form ofbridge. Figs. 2, 3, 4, and 5 are similar views showing modifications ofmy invention.

T T are through -spans. D D are deckspans. PP are piers. WV WV arewater-lines, G G ground-lines, and R R are rail or road way elevations.

Several combinations of through and deck spans might be devised under myinvention to suit different conditions; but those forms shown are themost important. Three spans are shown in all of the figures; but acombination with only two spans can be made. For example, one end of thethrough-span in Fig. 1 might rest ona pier. From the nature of acontinuous girderit is essential that there should be at least twospans. Continuous girders of this class are preferably made with hingedpoints of contraflexure.

Continuous-girder bridges where they span wide openings are lighter thanseparate spans to cover the same openings and may be made narrower, thussaving masonry through shortening the piers and admit of special modesof The employment of the deckerection, resulting often in great savingin the cost of the bridge. The latter is usually the determining factorin the question of their use. The advantages which the forms I proposehave over those forms of bridges in common use are a saving in masonryand increased facilities of erection.

Where draw-bridges are not used, navigation requires that openings of aspecial clear height shall be made under the bridge. The width of thisclear height required for steamboats is not great; but when in riverslike the Ohio and Mississippi large tows of barges and rafts must beaccommodated the span in which the maximum height occurs should be aswide as possible to accommodate such boats, rafts, and other floatingcraft. The high opening is of course over the channel. WVithout such aconstruction, as shown in Fig. 1, it would be necessary to use a singlethrough span over the central opening, attended with great expense anddanger of erection, or a through continuous girder running all of thepiers up. The latter would obviously be attended with greatly increasedcost of masonry and erection. Fig. 1 is especially applicable where achannel-span is required over deep water. The side spans D between thepiers would beerected on false work and then extended or built over thepiers as cantalevers without false work, as at d. The cantalever ends (6would serve as supports for temporary trusses 011 which to erect thethrough-span T, with probably no false work in the water, or at mostonly a temporary pier in the middle. In rivers where ice gorges occurthis is very important. The through-span T of this figure is an entirelyindependent span, preferably resting 011 the cantalevers as it wouldrest on piers, and is comparatively free from the temperature strainscommon to continuous girders.

Fig.2 is for a case where two side-channel through-spans T T are usedand the middle deck-span D is erected on false work in shallow Water,the ends 61 extended over the piers, and the through-spans erected uponthem, as in Fig. 1.

Fig. 3 is for a case where a very wide and high opening is required overthe channel and the side spans are made deckto save masonry and falsework.

Fig. 4 is for a case where two contiguous high openings are required.

In the case of Fig. 5 We have a construction very similar to that shownin Fig. 1, except that the connections between the deck and throughspans are somewhat different.

By the employment of my invention I am enabled to greatly cheapen thecost of the bridge as an entirety and at the same time obtain all theexisting advantages of the present modes of construction.

In all of the cases illustrated it would be necessary to usethroughspans throughout with the present style of continuous girder.

Having now described my invention, what I claim as new, and desire tosecure by Letters Patent, is

1. In a continuous-girder truss bridge, the combination of deck andthrough spans with two supporting-piers for at least one of said spans,and in which one of the spans is supported upon the end of the other.

2. In a continuous-girder truss bridge, the combination of deck andthrough truss-spans connected end to end with at least twosupporting-piers for each of one or more of said spans arranged at adistance from the juncture of the through and deck spans.

3. In a truss bridge, the combination of four piers arranged in pairs,two deck trussspans each with a cantalever projection, and eachsupported upon a pair of said piers and having their cantaleverprojections extending toward each other, and a through truss-spanarranged between said deck-spans and supported upon said cantaleverprojections.

, 4. 111 a truss bridge, the combination of four piers of substantiallythe same height arranged in pairs, two deck-spans, each with acantalever projection and each supported upon a pair of said piers andhaving their cantalever projections extending toward each other, and athrough truss-span arranged between said deck-spans and supported uponsaid cantalever projections at their extreme ends by a movable joint.

5. In a truss bridge, the combination of a pair of short piers, a decktruss-span supported upon said piers and having a cantalever projectionupon one end extending beyond the piers, and a through truss-span havingits end connecting with the end of the cantalever and resting thereon,whereby the same water-way is partly covered by a deck and partly by athrough truss-span.

6. In a truss bridge of the continuous-girder type, the combination of adeck truss-span having a cantalever projection, a supportingpier forsaid deck-span at one end, and also a second supporting-pier for thesaid span at a distance from its other end, and athrough truss-spansupported upon said cantalever at its place of contraflexure.

7. The combination of two pairs of piers or abutments, -twocantalever-trusses supported each upon a pair of said piers or abutmentsand overhanging said piers, so as to extend toward each other, and athrough-span supported upon the upper surface of said cantalevers.

' In testimony of which invention I hereunto set my hand.

GEO. H; PEGRAM. Witnesses:

ROBERT M. FUNKHOUSER, B. R. PEGRAM.

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